1. Field of the Invention
The invention relates in general to a semiconductor technology, and more particularly to an interconnection process.
2. Description of the Related Art
As the dimension of the integrated circuit (IC) element is getting smaller, the aspect ratio of the contact hole in the dielectric layer during the interconnection process increases accordingly, making it more difficult to maintain the quality of local interconnection.
Let the interconnection process using tungsten for local interconnection and having a contact hole whose aperture is larger than 0.2 micrometer (μm) be taken for example. Normally, a stacking layer containing titanium/titanium nitride (Ti/TiN) is formed via physical vapor deposition (PVD) technology to be used as the barrier layer and the adhesion layer for the conductive layer (tungsten) subsequently formed. As the aperture of the contact hole reduces, the aspect ratio increases, and the open problem occurring to PVD technology is even worse. The ionized metal plasma (IMP) technology using metallic organic chemical deposition (MOCVD) technology has the advantage of increasing the coverage rate at the bottom of the contact hole, but still has over-hang phenomenon and the problems that the MOCVD titanium nitride film contains too many impurities like carbon, hydrogen and oxygen.
Currently, the interconnection process using chemical vapor deposition (CVD) with TiCl4 can achieve better quality in the overall manufacturing process. For example, better coverage conformality is achieved, and the filming resistance of the stacking layer is within an acceptable range and the cost is cheaper. However, the titanium-silicon compound formed from the reaction between the stacking layer and the silicon base is still lack of uniformity.